recently i have odd behaviors with my google map demos on jsfiddle also. seems to me the rendering doesn't refresh very well. so, what i did is after applying changes to map i "refresh it" with map.setCenter(<new latlng>); and then re-zoom. Furthermore, the issue seems deal with any overlay on the map.
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kjy112Apr 25 '11 at 16:20

This turned out to be the issue for me too. The API generates different elements for Firefox and Chrome, so you can't use Firebug. To find out what style is giving you trouble in IE, use the IE7 browser mode, and be sure to hit the refresh button in the Developer Tools toolbar after the map loads. That will refresh the DOM and let you select the marker image to inspect it. Use the Trace Styles pane to find the offending style.
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JerphSep 22 '11 at 15:20

We were having problems with Google Maps API Version 3.8 (newer than several others who proposed solutions here). The custom markers would be cut off, while the default markers were not. We discovered that this was caused by the new Canvas tiles that are used to optimize how Google Maps display. If you inspect elements, you can see that the markers are actually tile layers.

If we turned off 'optimized' (see code below) the markers displayed correctly! So it appears to be related to the optimization code.